1. Field of Invention
The present invention relates to active matrix display devices. More specifically, the invention relates to an active matrix display device in which active elements are formed on a first substrate, wiring lines are formed on a second substrate, electro-optical elements are formed on a third substrate, an element chip having at least one active element is peeled off from the first substrate and is transferred onto the second or third substrate, and the second substrate is attached to the third substrate. Further, the present invention relates to a thin film transistor display device, where the active elements of the active matrix display device are thin film transistors.
2. Description of Related Art
In a related art active matrix display device including active elements, such as thin film transistors, wiring lines between active elements, and a supporting substrate, the active elements can be a part of the display device, and the remaining part of the display device can include the wiring lines and the supporting substrate. When, in the manufacturing process of the active matrix display device, active elements, wiring lines, and a substrate are formed as one body by the same process, a complicated manufacturing process is required in order to make active elements with high performance. Therefore, the manufacturing cost is expensive. However, the wiring lines and the supporting substrate do not require such a complicated and expensive manufacturing process and therefore are manufactured at a low cost. If active elements are manufactured separately from the wiring lines and the supporting substrate and the active elements can be arranged only on the necessary portion, the overall manufacturing cost for the active matrix display device can be reduced.
The related art includes an active matrix display device including: active elements formed on a first substrate, wiring lines formed on a second substrate, and an element chip having at least one active element peeled off from the first substrate and then transferred onto the second substrate. The related art also includes a thin film transistor display device, in which active elements of the active matrix display device are thin film transistors. According to the above-mentioned description, it is possible to arrange active elements only on the necessary portion, thus reducing the overall manufacturing cost of an active matrix display device or a thin film transistor display device. Further, in this case, an adhesive or laser ablation is used in the separating and transferring processes.
FIG. 1 shows a manufacturing method of an active element and an element chip according to the related art. The active element is a thin film transistor. A peeling layer 12 is formed on a first substrate 11, and an underlying insulating film 13 is formed on the peeling layer 12. An amorphous silicon (a-Si) film 14 is formed on the underlying insulating film 13 by PECVD of SiH4, or LPCVD of Si2H6, and a polysilicon (poly-Si) film is obtained by laser crystallization 15 and is patterned to obtain an active layer 16. A gate insulating film 17 is formed by PECVD or ECR-CVD of TEOS, and a gate metal film is formed thereon and is patterned to obtain a gate electrode 18. P-ions and B-ions are selectively implanted using a resist mask 1a by ion implantation or ion doping 19 to form a source and drain region 1b. A first interlayer insulating film 1c is formed, and then a first contact hole 1d is formed. A source and drain metal film is formed and is patterned to obtain a source and drain electrode 1e. Accordingly, a CMOS thin film transistor including an n-type thin film transistor 1f and a p-type thin film transistor 1g is obtained. Further, a second interlayer insulating film 1h is formed, and then a second contact hole 1i is formed. A pad metal film is formed and is patterned to obtain a connection pad 1j. Finally, separations 1k to separate element chips are formed. Even though only one element chip is shown in FIG. 1, a plurality of element chips is actually arranged.
FIG. 2 shows a method of separating and transferring an element chip according to the related art. As mentioned above, a peeling layer 22 is formed on a first substrate 21, and a thin film transistor 23 and connection pads 24 are formed on the peeling layer 22 to form an element chip 25. Wiring lines 27 and connection pads 28 are formed on a second substrate 26, and an adhesive 29 is applied thereon. Then, the first substrate 21 and the second substrate 26 are press bonded to each other by the adhesive 29 to flow the adhesive and to electrically connect the connection pads 24 of the element chip 25 to the connection pads 28 of the second substrate 26. The adhesive 29 does not flow to adjacent element chips 25, owing to separations 2a. An element chip 25 having at least one thin film transistor 23 is peeled off from the first substrate 21 by laser ablation using an irradiating laser 2b and is then transferred onto the second substrate 26.
FIG. 3 is an enlarged view showing a transferred element chip according to the related art. In FIG. 3, connection pads 33 of an element chip 31 having at least one thin film transistor 32 are electrically connected to connection pads 36 of the second substrate 34 having wiring lines 35 formed thereon (for example, as disclosed in T. Shimoda, et al, Techn. Dig. IEDM 1999, 289, S. Utsunomiya, et al, Dig. Tech. Pap. SID 2000, 916, T. Shimoda, Proc, Asia Display/IDW '01, 327, S. Utsunomiya, et al, Proc. Asia Display/IDW '01, 339).